Tesla is planning major upgrades for its plant in Austin, Texas, according to filings made with the Texas Department of Licensing and Registration in January.

First reported on Tuesday by the Austin Business Journal, the filings indicate Tesla plans to invest $717 million in the site to add around 1.4 million square feet of space.

Four new buildings were mentioned in the plans, including for battery cell development and production, cathode and drive unit production, and a die shop.

The plant is where Tesla builds the Model Y for the eastern part of the U.S., and the recently launched Semi truck. Tesla also plans to build its Cybertruck pickup truck at the site, production of which is expected to start later this year.

Tesla also has its original vehicle plant in Fremont, California, as well as vehicle plants in Berlin and Shanghai. The company also has a plant in Reno, Nevada, which builds battery packs and other components.

The company is thought to be planning at least two more plants. One will be a second plant in Shanghai to take capacity there to more than a million vehicles per year. Tesla mentioned the second plant in a letter last May sent to officials in Shanghai's Lingang Special Area, where the existing Shanghai plant is located.

Another plant may be built in Mexico. Bloomberg reported last month that Tesla is close to announcing plans to build a plant in the automotive hub of northeastern Mexican state Nuevo León.